| Nanocomposite ceramics have excellent mechanical properties at both ambient andelevated temperatures, which makes them widely used in cutting-tools, bearing and enginecomponents, et al. Al2O3-ZrO2-MgAl2O4 nanocomposite ceramic has high hardness, excellentdielectric and sintering properties, as well as high toughness and superplasticity.Using the sol-gel method to prepare the Al2O3 based nanocomposite powders, theinfluence of PH, initial concentration of the solution, calcination temperature, surfactant, theration of alcohol to water and the dispersant agent on the particle size, distribution,agglomeration state of the powders were studied. The obtained nano-composite powders haveuniform particle size and good distribution of phases. The average particle size ofas-synthesized powders is about 20nm in average, no hard agglomeration. The results ofX-ray Diffraction(XRD) and the thermogravimetric-differenrial thermal analyses (TG-DTA)for powders after calcinating at different temperature show that the powders mainly consist ofAl2O3, ZrO2 and MgAl2O4 phases. The as-calcined powders at 1000℃is relatively stableduring calcinating at elevated temperatures.The process of the hot-pressing sintering of Al2O3-ZrO2-MgAl2O4 is presented in thispaper. The measurement of relative density and average grain size of as-sintered materialsshows that the proper sintering temperature is 1450-1500℃. The SEM observation indicatesthat the fracture surface of the as-sintered sample is mainly of intergranular andtranscrystalline fracture, the grain profile and the similar dimple after grain pulling can beseen clearly at 1450℃. After hot pressing sintering, the relative density of as-sinteredAl2O3-ZrO2-MgAl2O4 is up to 98.1%, which shows that the hot-pressing sintering is aneffective sintering method to prepare this nanocomposite ceramic.The superplastic compressive tests of as-sintered Al2O3-ZrO2-MgAl2O4 three phasesnanocomposite ceramic demonstrate that this material behaves good deformability at 1500℃,its compressive deformation reaches 60%. The comparison of the phase variation, elementdistribution, microstructure and mechanical properties demonstrates that the mechanicalproperties of deformed specimens is almost as well as that of the as-sintered specimens. Aftersuperplastic deformation the maximum microhardness is 32 GPa, which is slightly lower thanthat of the undeformed specimens of 35 GPa. And its fracture toughness is 6.85 MPa·m1/2, which is slightly lower than of the as-sintered specimens of 6.96 MPa·m1/2. However, afterdeformation its resistivity to load was heighten. |
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